Sideseam joint for a carton

ABSTRACT

Unwanted adhesion between a second panel and a first panel attendant the formation of the sideseam joint is eliminated by providing the second panel with a notch. The notch corresponds in form to the triangular notch or truncated portion at the tapered end of the sideseam forming fifth panel. In this way, when compression of the first panel against the sideseam panel occurs, there is no hot and sticky exposed area of the first panel which will adhere to the second panel.

This application is a continuation of Ser. No. 09/928,359, filed on Aug.14, 2001, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to paperboard containers of the type often usedfor the packaging of liquids such as milk and fruit juices. Suchcontainers are fashioned from a unitary blank of paperboard, usuallycoated on both its interior and exterior surfaces with one or morebarrier layer materials, cut and scored, erected and filled on automaticmachinery to form gable top liquid packages. Such containers have a flatbottom and a gable top upper or roof section, the latter being adaptedto form a pour spout when opened, all as known. An intermediate step inmaking such containers is the formation of a tube structure from theblank, with the steps of forming the end closures and filling withliquid taking place after tube formation.

In the formation of a gable top containers from a unitary blank having aplurality of wall forming panels serially arranged, one step involvesforming a tube by folding the blank so that the fifth or sideseamforming panel is superposed over an edge zone of the free edge portionof the first sidewall forming panel. A part of the carton interiorforming surface of the first panel has been heated so as to partiallymelt the usual polyethylene coating and make the latter sticky.Similarly, that portion of the fifth or sideseam panel which is to be insurface contact with the first panel free edge zone has also been heatedso as to make its polyethylene coating sticky. The transverse crosssectional configuration of the now folded blank is substantially that ofa shallow diamond, with a force applied to the upper two panelscollapsing the diamond shaped tube, resulting in a force applied to thesideseam flap or panel to seal it to the edge zone portion of the firstpanel.

Often, the sideseam is skived, with the particular skivingprocess/apparatus employed unavoidably resulting in a taper at one endof the sideseam forming or fifth panel, at the bottom carton closure.This taper causes a partial triangular uncovering of the first paneledge zone, so that when the panels are pushed downwardly to compress andseal the sideseam (fifth) panel against an edge zone of the fist panel,a portion of the second panel will contact an exposed hot and stickytriangular portion of the first panel and cause an unwanted adhesionbetween a triangular portion of the first panel, near the tapered end ofthe sideseam panel, and the triangular portion of the second panel.

In order to avoid unwanted adhesion, the temperature of the heated firstpanel edge portion and the temperature of the fifth or sideseam formingpanel is reduced to decrease the stickiness. While solving the problemof unwanted adhesion, such temperature reduction diminished the strengthand quality of the seal between the sideseam panel and the first panel.This lowered quality becomes unacceptable with extended shelf lifeliquid cartons.

SUMMARY OF THE INVENTION

According to the practice of this invention, the noted unwanted adhesionbetween the second panel and the first panel attendant the formation ofthe sideseam joint is eliminated by providing the second panel with anotch. The notch corresponds in form to the triangular notch ortruncated portion at the tapered end of the sideseam forming fifthpanel. In this way, when compression of the first panel against thesideseam panel occurs, there is no hot and sticky exposed area of thefirst panel which will adhere to the second panel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a prior unitary paperboard blank for forming agable top liquid carton;

FIG. 2 is a perspective view of the tubular carton being collapsed;

FIG. 3 is a plan view of a unitary blank of paperboard provided with anotch in the first panel;

FIG. 4 is a perspective view of a tubular carton formed form the blankof FIG. 2 being collapsed;

FIG. 5 is a plan view of a unitary blank of paperboard provided with anotch in the second panel; and

FIG. 6 is a perspective view of a tubular carton formed form the blankof FIG. 5 being collapsed;

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, a unitary paperboard 10 includes first, second,third, and fourth sidewall forming panels and a fifth, sideseam formingpanel. These panels are denoted as 12, 14, 16, 18, and 20 respectively.The upper ends form a gable top when folded and erected, while the lowerends of the panels form a bottom closure. The lower ends are formed byfirst 112, second 114, third 116 and fourth 118 panels. Each closurepanel is connected to a sidewall panel by a fold line. The second 114and fourth 118 panels each contain a pair of diagonal fold lines, as isconventional. Tab 24 is conventional, and taper 28 is formed during theleft or free edge skiving of fifth or sideseam forming panel 20. Taper28 is formed as the bottom edge of the sideseal panel 20 extendsupwardly from the fold line between the panel 20 and the fourth closurepanel 118.

Right edge zone 40 of first panel 12 denotes a sealing area thatcontacts sealing panel 20 when the blank in folded into a tube form. Animaginary triangular zone, later to be described, is bounded byimaginary lines 32 and 34. Both surfaces of the blank are provided withbarrier layer coatings, such as polyethylene, as is conventional.

FIG. 2 illustrates a step in the formation of a tube from paperboardblank 10 for forming a gable top container. The paperboard blank isfolded to have sideseam panel 20 overlap a part or zone 40 of the edgeof panel 12. Prior to this, the lower surface of sideseam forming panel20, as viewed at FIG. 2, has been heated, as by flame or othertreatment, as has been that portion of panel 12 (see area 40 of FIG. 1)which will be in surface contact with sideseam panel 20. These twoheated surfaces are at a higher temperature (not necessarily the same)than their respective surfaces on opposite sides of the blank. Secondpanel 14 and third panel 16 are now pressed downwardly, so that panel 14overlies panel 12. This presses the heated surface of sideseam formingpanel 20 against the locally heated edge portion 40 of first panel 12.The thermoplastic on these portions of panels 20 and 12, because theyhave been heated, are tacky, resulting in a joint or seam between firstpanel 12 and sideseam panel 20.

By virtue of taper 28 on sideseam forming panel 20, a triangular zone 30on first closure panel 112 heated with the rest of the free edge portionof panel 12 is exposed. Accordingly, when panels 14 and 16 are pusheddownwardly to apply pressure to form the sideseam joint or seam betweenpanels 12 and 20, a corresponding portion 30A of second closure panel114 becomes adhered to the hot and sticky triangular portion 30 of panel112. This adhesion renders the tube unusable for further processing intoa gable top carton. In the past, only lowering the surface thermoplastic(typically polyethylene) softening temperature of panels 12 and 20eliminated the problem, but at the cost of an inferior sideseam joint.

Referring now to FIG. 3, the blank of U.S. Pat. No. 5,626,285 is shownand differs from the blank of FIG. 1 only by a notch formed by theremoval of a triangular zone bordered by cut lines 34 and 36 from thebottom edge of the closure panel 112 extending from first panel 12.

Referring now to FIG. 4, it is seen that when panels 14 and 16 arepressed downwardly to form the sideseam joint, there will be no zone orportion of panel 112 beyond taper 28 which will stick to panel 114 atregion 30A. Thus, what is shown at FIG. 4 is conventional, except forcut lines 34 and 36 and the consequent absence of triangular zone 30 ofFIG. 2. The notch shown at FIGS. 3 and 4 is bordered by lines 34 and 36and is triangular. FIG. 4 shows edges 28 and 34 as coincident. Ifdesired however, cut line 36 could be curved or could extend straightdownwardly, parallel to the edge of zone 40, instead of at an angle asshown at FIG. 3. As earlier stated, in practice the seam forming stepshown at FIGS. 2 and 4 is carried out with the tube formed from thesidewalls and the fifth panel 20 rotated 180 degrees about itslongitudinal axis.

When the carton described in U.S. Pat. No. 5,626,285 is utilized insmall sized cartons, a difficulty has been encountered in forming thebottom of the carton prior to filling with automated machinery. Thenotch in the first panel has a tendency to prevent the clean folding ofthe gable tips formed in the second and fourth panels. It is thereforeadvantageous to move the notch from the first panel to the second panelbut still in a position corresponding to the exposed glue on the firstclosure panel 112 formed by the truncation of the sideseam panel.

Referring now to FIG. 5, the blank of the invention is seen. The secondclosure panel 114 has a free edge 144 opposite the fold line between thesecond closure panel 114 and second panel 14. The third closure panel116 has a free edge 146 opposite the fold line between the third closurepanel 116 and second panel 16. The second closure panel 114 has a notchdefined by edges 134, 136 in its bottom edge. Edge 134 extends from freeedge 144 and joins edge 136. The edge 136 extends from the end of edge134 to the free edge 146 of third closure panel 116. The notch removesmaterial from the second closure panel that would otherwise adhere tothe exposed adhesive 30 on the first closure panel 112 when the blank isformed into a collapsed tube. Edge 136 corresponds to a line 34demarcating the truncated edge 28 of the glue flap 20 after it is joinedto the first panel 12 to form a tubular carton.

FIG. 6 depicts the tube being flattened and the notch overlying theexposed glue area 30 created as the sideseam panel 20 overlies the gluearea 40 of first panel 12. The free edge 136 of the notch corresponds tothe truncated edge 28 of the glue flap 20 so that the exposed adhesivearea 30 does not come in contact with the portion of the second panel ofthe carton 14. In this way, unwanted adhesion of the flattened tube isprevented. When flattened, the first and fourth panels 12, 18 form alower layer and second and third panels 14 and 16 form the upper layer.The upper layer, specifically second panel 14, does not have materialthat may become adhered to the lower layer. The carton is shipped inthis configuration until its ultimate formation into a carton filled andsealed.

While the invention has been described in the preferred embodiment,modifications and variations would be obvious to one of ordinary skillin the art without departing from the spirit of the invention. Thedescription is not intended to be eliminating in any way, but is definedby the appended claims.

1. A blank for forming a container, comprising: a first panel connected to a second panel along a first fold line, said second panel connected to a third panel along a second fold line, said third panel connected to a fourth panel along a third fold line, said fourth panel connected to a fifth panel along a fourth fold line, a first, second, third and fourth closure panel connected to said first, second, third and fourth panels, respectively, by fold lines, said second closure panel having a free edge opposite said fold line between said second panel and said second closure panels, said third closure panel having a free edge opposite said fold line between said third panel and said third closure panels, said fifth panel having a bottom edge extending upwardly from said fourth fold line, and a notch in said free edge of said second panel, said notch formed by a first edge extending from said second closure panel free edge and a second edge extending upwardly from third closure panel free edge.
 2. The blank of claim 1, wherein said second edge extends passed a fold line between said second closure panel and said third closure panel.
 3. The blank of claim 1, wherein said blank is made of paperboard.
 4. A collapsed tube for forming a container, comprising: a first closure panel connected to a second closure panel along a first fold line, said second closure panel connected to a third closure panel along a second fold line, said third closure panel connected to a fourth closure panel along a third fold line, said fourth closure panel connected to a fifth panel along a fourth fold line, said fifth panel having a bottom edge extending upwardly from said fourth fold line, said fifth panel adhered to said first closure panel, said second panel overlying said first panel, an area of exposed adhesive on said first panel below said fifth panel, and a notch in said second closure panel corresponding to the portion of said second closure panel overlying said area of exposed adhesive.
 5. The tube of claim 4, wherein said area of exposed adhesive is triangular.
 6. The tube of claim 4, wherein said notch is formed by a first edge and a second edge, said second edge overlying said fifth panel bottom edge. 